1. Field of the Invention
The present invention relates to a semiconductor device and a process for producing the same. The present invention is used, for example, for a semiconductor device comprising a plurality of elements formed on one substrate, the elements being separated from each other for insulation.
2. Description of the Related Art
The applicant of the present invention has previously filed a patent application, i.e., U.S. patent application Ser. No. 07/597,698, directed to a semiconductor device comprising a plurality of elements formed on one substrate, the elements being separated from each other for insulation.
This semiconductor device is an apparatus developed for preventing the occurrence of noise from adjacent semiconductor elements formed on the substrate. In this device, a conductive layer is formed so as to surround an element forming region where a semiconductor element comprising an SOI (silicon on insulator) device is formed, and an SiO.sub.2 film is formed as an insulating film around the conductive layer to utilize the conductive layer as an electric shielding layer.
In the above-described U.S. patent application Ser. No. 07/597,698, however, it has been found that, since the SiO.sub.2 film is formed under the SOI layer, when a strain attributable to the thermal expansion coefficient difference occurs within the SOI layer, the strain brings about a crystal defect due to a reduction in the film thickness now in use.
A multilayer interconnection is one means used for solving this problem. In this means, to combat a tensile stress exerted by an interlayer-insulation film (SiO.sub.2 film) formed for insulating the (n)th layer from the (n+1)th layer, an Si.sub.3 N.sub.4 film is formed on or under the interlayer-insulation film to exert a compressive stress and thereby relieve the tensile stress.
In the use of the above-described technical means for solving the above-described problem it has been found that, when the Si.sub.3 N.sub.4 film is formed on the SiO.sub.2 film, since the element forming region and the Si.sub.3 N.sub.4 film are in direct contact with each other, the compressive stress of the Si.sub.3 N.sub.4 film acts on the element forming region, and thus a crystal defect occurs within the element forming region.